1. Field of the Invention
This invention relates to cement compositions which comprises a filler, a binder to be used in admixture with the filler, and a curing agent for polymerizing the binder. This invention can be suitably but not exclusively applied to dental restorative materials, such as dental composite filling materials, crown bridge materials, artifical tooth materials, dental cementing materials etc., and other medical materials, such as bone cementing materials and the like, among which it is preferably applicable to dental composite filling materials, and therefore this invention will hereinbelow be described in particular reference to this field within limits not prejudicial to generality.
2. Description of the Prior Art
Dental restorative materials are composed of a mixture of a fine particulate filler as a main component, a polymerizable monomer as a binder, and a curing agent for curing the polymerizable monomer. Such materials are filled in tooth cavities and subsequently cured, or are cured and molded into predetermined shapes before being fixed on tooth.
In the field of dental composite filling materials, there have heretofore been employed, as the binder, monomer mixtures obtained by diluting 2,2'-bis[p-(.gamma.-methacryloxy-.beta.-hydroxypropoxy)phenyl]propane (hereinafter referred to as Bis-GMA) with a monomer such as triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate etc. Such dental composite filling materials are described in detail in e.g. U.S. Pat. Nos. 3,066,112, 3,926,906 etc., but such conventional dental composite filling materials suffer from considerably low compressive strength and abrasion resistance, and thus they have merely been employed only for filling anterior teeth where mechanical properties are not so required.
In order to increase copressive strength, extensive studies on binder monomers have been conducted. For example, U.S. Pat. No. 3,721,644 discloses that tetra-functional methacrylate monomers having a backbone of bisphenol A have a favorable effect on compressive strength. However, since their handling was difficult due to their high viscosities, it was impossible to add such fillers to high levels. Further, U.S. Pat. No. 3,845,009 discloses that tetra-functional methacrylate compounds having a backbone of phenol have a favorable effect on compressive strength. However, they were far from those for practical use.
Among various (meth)acrylate compounds employed as binders in dental composite filling materials are urethane acrylate monomers, which are disclosed in U.S. Pat. Nos. 3,862,920 and 3,931,678. In these U.S. Pat. Nos., attention was drawn to that the urethane acrylate monomers have adhesion to tooth cavities, but specific disclosure thereof was restricted to di-functional and tri-functional ones, which did not impart high compressive strength or abrasion resistance.